A total of 565 women was partioned in four groups: the control group with 155 women, who started the sexual life without any contraceptive control; group I, with 162 women who had been taking oral contraceptive during a period of one year, starting at the beginning of their sexual lifes; group II, with 127 women who had "been taking the same oral contraceptive during a period of 2 years starting at the beginning of their sexual lifes; group III, with 121 women who repeated the same procedure during a period of 3 years. All the 565 women had the same social economic status and the same health conditions; were between 19 and 25 years old and used the contraceptive in a same way. The frequency distributions of time required for conception showed a clear difference between groups control and I as compared to groups II and III. The analysis of variance confirmed the difference. Based on these results, it is concluded that oral hormonal contraceptive after the second year of continous use interfer with the reproductive system, this determining a larger time required for conception.